The steady increase in the need for refined products has led to a dependency on heavy crude oil to meet the rising demand. Heavy crude oils are available at a significant discount to light, sweet crudes (oils with low hydrogen sulfide and carbon dioxide contents, usually containing less than 0.5% sulfur) and can yield significantly more processable residue.
However, heavy crude oils may contain impurities, and may have a metal content, sulfur content, or aromatic content that is unsuitable in some industrial applications. For these reasons, pretreatment steps to upgrade the heavier crude oil are usually required. The pretreatment methods can be classified into two main groups: solvent extraction, and hydroprocessing.
An example of solvent extraction includes the ROSE® (Residuum Oil Supercritical Extraction) solvent extraction process, developed by Kellogg Brown & Root, Inc. The ROSE process is a solvent deasphalting (SDA) process that separates a resin fraction from asphaltene. However, the ROSE process demonstrates poor conversion of the vacuum residue and thereby is not an economically feasible process. Specifically, to reduce the metal content of the vacuum residue of Arabian heavy crude oil from 250 weight parts per million (wt ppm) to 9 wt ppm by the ROSE process, over 50% of vacuum residue is rejected as asphaltene pitch. Therefore, the ROSE process is not an effective deasphalting oil process because it rejects so much of the vacuum residue.
Hydroprocessing reactions may also be utilized to reduce asphaltene using a supercritical water process. Hydroprocessing uses hydrogenation reactions in the presence of a catalyst and an external supply of hydrogen as a post-treatment process. However, a hydroprocessing unit requires a significant investment and consumes a considerable amount of externally-supplied hydrogen. Additionally, asphaltene present in oil may plug the pores of the catalyst, causing operational problems and increasing costs. Therefore, hydroprocessing is also an ineffective deasphalting oil process.